(a) Field of the Invention
The present invention relates to a vertically aligned liquid crystal display, and more particularly, to a vertically aligned liquid crystal display having a aperture pattern formed in electrodes to obtain a wide viewing angle.
(b) Description of the Related Art
A liquid crystal display (LCD) is structured having liquid crystal injected between an upper substrate having a common electrode and a color filter, and a lower substrate having thin film transistors and pixel electrodes. A voltage of a different potential is applied to the pixel electrodes and common electrode to form an electric field, thereby varying the alignment of liquid crystal molecules of the liquid crystal material. In this way, the transmittance of incident light is controlled to display images.
In a vertically aligned (VA) LCD, long axes of the liquid crystal molecules align themselves vertically to the substrates in a state where no electric field is formed between the substrates. The VALCD has a high contrast ratio and a wide viewing angle such that this LCD configuration is the most commonly used type of liquid crystal display.
In one method to obtain a wide viewing angle in the VA LCD, aperture patterns are formed in the electrodes. With this configuration, a fringe field is used to uniformly scatter a slanting direction of the liquid crystal molecules into four directions to achieve a wide viewing angle. A conventional VA LCD, having aperture patterns formed in the electrodes to obtain a wide viewing angle, will now be described with reference to FIG. 1.
FIG. 1 shows a partial sectional view of a conventional VA LCD having aperture patterns formed in electrodes.
A pixel electrode 110 is formed on an insulating lower substrate 100, and a common electrode 210 is formed on an insulating upper substrate 200. Aperture patterns are formed in the pixel electrode 110 and the common electrode 210. Apertures of the aperture pattern of the pixel electrode 110 are provided alternately with apertures of the aperture pattern of the common electrode 210. Further, liquid crystal material is injected between the substrates 100 and 200 to form a liquid crystal layer 300.
As shown in the drawing, a fringe field generated by the aperture patterns uniformly controls a slanting direction of liquid crystal molecules of the liquid crystal layer 300. A wide viewing angle is realized as a result. However, at center portions between apertures of the upper substrate 200 and the lower substrate 100, weak fringe field forms an area by the vertical electric field with respect to the substrates where the liquid crystal molecules do not quickly change alignments by the electrical field. Also, the liquid crystal molecules in these areas begin to slant only after liquid crystal molecules in the vicinity of the aperture patterns are slanted. This slows down the response speed of the LCD.
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a vertically aligned liquid crystal display in which a lower and an upper aperture pattern are formed in electrodes of at least one substrate to form a stepped pattern at the center of the aperture pattern. Accordingly, a response speed is improved.
To achieve the above object, the present invention provides a liquid crystal display comprising a first substrate made of an insulating material; pixel electrodes formed on the first substrate, the pixel electrodes having a first aperture pattern; a second substrate made of an insulating material and provided opposing the first substrate at a predetermined distance; a common electrode formed on the second substrate, the common electrode having a second aperture pattern; and a liquid crystal layer made of liquid crystal material injected between the first substrate and the second substrate, wherein either or both of the pixel electrodes and the common electrode include stepped portions, which protrude a predetermined distance away from the substrates, between apertures of the first and/or second aperture patterns.
According to a feature of the present invention, the pixel electrodes include the stepped portions.
According to another feature of the present invention, the stepped portions are formed by providing the pixel electrodes over a gate insulation layer and a protection layer.
According to yet another feature of the present invention, the common electrode includes the stepped portions.
According to still yet another feature of the present invention, the pixel electrodes include first stepped portions and the common electrode includes second stepped portions.
According to still yet another feature of the present invention, the first stepped portions and the second stepped portions are provided in a sequence of the first aperture pattern, the second stepped portions, the first stepped portions, and the second aperture pattern.
According to still yet another feature of the present invention, the liquid crystal display further comprises thin film transistors formed on the first substrate, the thin film transistors switching image signals transmitted to the pixel electrodes.